A mass spectrometer is one type of device for analyzing components contained in a liquid sample. A mass spectrometer includes an ion source for ionizing components in a liquid sample and a mass spectrometry section for separating and detecting the ionized components according to their mass-to-charge ratios. In an ion source for ionizing a liquid sample (e.g. ESI source or APCI source), the ionization of a liquid sample is normally achieved by supplying the liquid sample to an ionization probe and making an atomization-promoting gas (which may also be called a “nebulizer gas” or “drying gas”) blow at the liquid sample exiting from the tip of the ionization probe.
For example, a liquid sample introduction system described in Patent Literature 1 is used to introduce a liquid sample into the previously described type of ion source. In this liquid sample introduction system, a liquid-supply gas is sent into the space above the liquid surface in a hermetically closable container holding a liquid sample (liquid sample container) to supply the liquid sample from the liquid sample container to the ionization probe of the ion source by the pressure of the liquid-supply gas.